The present invention relates in general to security systems for motor vehicles and, more particularly, to security sensor system apparatus and methods of operating that apparatus in a motor vehicle security system wherein the sensor system augments the security system by detecting glass breakage and intrusion into the interior of the motor vehicle without opening a door or other entry point.
A variety of motor vehicle alarm systems are known in the art. The common goal of all these alarm systems is to secure the vehicle from unauthorized intrusions once the vehicle has been closed and locked. Typically, motor vehicle alarm systems secure at least the interior of the vehicle or the passenger compartment by sensing the status of entry points into the passenger compartment. Such alarm systems perform what is referred to as perimeter sensing which is conveniently performed by monitoring door sensors or switches provided, for example, to light up the interior of a vehicle when one or more of its doors are open. Additional sensors may be provided to monitor opening of a hatchback, hood, trunk, sunroof and possibly even a fuel door. When any of the sensors detect opening of the associated entryway into the vehicle, a signal is sent to a centralized alarm control unit.
If the control unit is armed, it generates an alarm signal which in turn activates an alarm. The alarm may be visual for example by flashing the headlights of the vehicle and/or audible for example by activating the horn of the vehicle. In any event, the alarm is activated only for a limited time period prior to being reset. The alarm draws attention to the unauthorized access to the vehicle and is intended to scare off a would-be intruder who has caused the alarm signal to be generated. The alarm signal may also activate a communications system to alert a remote location such as a local police department, the vehicle owner, security personnel or the like of the intrusion.
More sophisticated alarm systems detect intruders who attempt to access or access the interior of a vehicle without opening doors, hatches or the like of the vehicle. Such systems can monitor the breakage of glass within a motor vehicle and generate an alarm signal upon glass breakage detection. Other systems detect such intruders by sensing motion or the presence of intruders within the interior of the motor vehicle. For example, ultrasonic energy systems are used to monitor for motion within the interior of a vehicle and D-field systems are used to monitor for the presence of an intruder. Electric fields generated within a vehicle by D-field systems are disrupted by the presence of an intruder.
Unfortunately, for reliable operation of known ultrasonic and D-field intruder sensors, a motor vehicle including an intruder sensor must be closed. Further, if a person or pet is present in the vehicle, the security system cannot be activated since the motion and/or presence of the person or pet would be sensed and result in a false alarm.
Accordingly, there is a need for an improved motor vehicle security sensor system for monitoring a motor vehicle and reliably detecting intrusions into the interior of the vehicle without opening the doors or other entryways into the vehicle. While the sensor system can stand-alone, preferably it would be used in combination with a perimeter security system to complement the perimeter security system and enhance vehicle security. Preferably, the sensor system would permit security system activation with persons and/or pets present in a vehicle interior for most vehicles, and would operate properly even if the vehicle was not closed but was ventilated by opening the windows by small amounts.